Capacitive seat occupancy detection and classification system

A capacitive seat occupancy detection and classification system, including

• an impedance measurement circuit, comprising:
• a signal voltage source that is configured for providing periodic electrical measurement signals at an output port, wherein a capacitive sensor is electrically connectable to the output port for receiving the electrical measurement signals, and wherein the signal voltage source is configured to generate periodic measurement signals of N different fundamental frequencies, wherein N is a natural number of at least 3,
• a sense current measurement circuit that is configured to determine complex sense currents that are being generated in the capacitive sensor by the provided periodic measurement signals of the at least N different fundamental frequencies,
• a signal processing unit that is configured to:
• determine a complex impedance from each of the determined sense currents with reference to a complex reference potential, and to
• provide output signals that are representative of the complex impedances determined at the at least N different fundamental frequencies,
• and
• a control and evaluation unit that is configured to:
• receive the output signals provided by the signal processing unit,
• compare each of the complex impedances determined at the at least N different fundamental frequencies to predetermined threshold values,
• based on the result of the comparing, determine a seat occupancy class for each one of the complex impedances determined at the at least N different fundamental frequencies, and to
• determine a final seat occupancy class derived at least in part by a majority among the seat occupancy classes determined for each one of the complex impedances determined at one of the at least N different fundamental frequencies,
• wherein N equals [(2×n)+1], with n being a natural number larger than 1 representing the number of potential resonances or electromagnetic (EM) narrowband interferences.